This invention relates to valves.
A variety of valve types are known. Most conventional types rely on a movable valve member that seals off an orifice or valve seat in the closed position while it moves off the seat during opening to allow flow through the orifice During closure the member is acted on by the pressure of the fluid so that the member has to press on its seat with a force which outbalances the pressure acting on the member and this force is constantly applied to the seat during closure.
Especially with float controlled valves this is a disadvantage. The larger the orifice and hence the force to be outbalanced, the larger the float and its lever arm have to be.
In many cases it would be an advantage to have a closure member held on a seat by means of a force which is independent of the pressure of the fluid to be controlled.